|Diaphorocetus poucheti (Moreno, 1892)|
in Paolucci, Buono, Fernández, et al., 2019.
Sperm whales (Physeteroidea) are the basal-most surviving lineage of odontocetes, represented today by just three highly specialized, deep-diving suction feeders. By contrast, extinct sperm whales were relatively diverse, reflecting a major Miocene diversification into various suction feeding and macroraptorial forms. The beginnings of this diversification, however, remain poorly understood. The Atlantic coast of South America provides a crucial window into early physeteroid evolution and has yielded some of the oldest species known from cranial material, Idiorophus patagonicus and Diaphorocetus poucheti – both of which are in need of re-description and phylogenetic reappraisal. Here, we re-examine Diaphorocetus in detail and, in light of its complex taxonomic history, declare it a nomen protectum. Phylogenetically, the species forms part of a polytomy including ‘Aulophyseter’ rionegresis and the two crown lineages (Physeteridae and Kogiidae) and demonstrates that facial asymmetry and a clearly defined supracranial basin have characterized this lineage for at least 20 Ma. With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known. Its cranial morphology hints at an intermediate raptorial/suction feeding strategy and it has a moderately developed spermaceti organ and junk.
Keywords: Physeteroidea, Gaiman Formation, phylogeny, anatomy, body size, Miocene
Cetacea Brisson, 1762
Neoceti Fordyce & de Muizon, 2001
Odontoceti Flower, 1867
Physeteroidea Gray, 1821
Diaphorocetus Ameghino, 1894 nomen protectum
Diaphorocetus poucheti (Moreno, 1892)
Florencia Paolucci, Mónica R. Buono, Marta S. Fernández, Felix G. Marx and José I. Cuitiño. 2019. Diaphorocetus poucheti (Cetacea, Odontoceti, Physeteroidea) from Patagonia, Argentina: One of the Earliest Sperm Whales. Journal of Systematic Palaeontology. DOI: 10.1080/14772019.2019.1605544